As of my last knowledge update in September 2021, flexible lithium-air (Li-Air) batteries were still largely in the research and development stage. At that time, there wasn't a standardized or typical voltage rating for such batteries since their development was ongoing and various research groups were exploring different approaches to making them.
Lithium-air batteries are known for their potential to achieve high energy densities due to the reaction of lithium with oxygen from the air. However, they also face significant technical challenges, such as issues related to stability, efficiency, and cycle life. Flexible versions of these batteries would have additional challenges related to maintaining their structural integrity and performance while being bent or deformed.
If there have been significant advancements in flexible Li-Air battery technology since September 2021, I might not be aware of those developments. I recommend checking recent scientific literature, news articles, or official announcements from research institutions or companies involved in battery research to get the most up-to-date information on flexible Li-Air battery voltage ratings.